Just as a shepherd must always worry about protecting their flock from the omnipresent danger of wolves, in the winery our primary concern is keeping the wine safe from a pervasive and invisible threat. This spoilage agent surrounds us, however, and in almost all other circumstances is necessary for life. I'm referring to oxygen, of course; O2, the eighth element, a molecule that makes up 20.946% of the earth's atmosphere by volume. You might think oxygen is something we would want to be on good terms with in the winery,* but the fact is that we spend nearly as much time restricting undesired oxygen contact with our wines as we do keeping things clean in the winery. That is a lot of time.
So what does this mean in terms of practical action in the winery? You are undoubtedly already familiar with one, long standing protection used in wineries and cellars: bungs in barrels. Not only does the bung prevent free contact between the wine and air, as liquid evaporates from the barrel the bung also allows for a vacuum to form in the space left behind rather than allowing oxygen to fill it in. If you come on a tour of our winery, you will similarly notice that all our tanks are topped with a barrel bung on top of the larger hatch at the top of the tank is sealed down to prevent oxygen ingress as well.
The oxygen threat is most severe when a wine from tanks or barrels is about to be racked, transferred, or filtered to a new (empty) tank in the cellar. In these cases the first task is to get the new tank entirely set-up and then find a way to get the oxygen out of it or prevent it from becoming an issue. In the US this often means connecting a gas cylinder to the bottom of the tank with a gas that is heavier than oxygen and then blasting the living daylights out of the tank for a significant amount of time. In New Zealand and Australia, the tank is often set-up and then a chunk of dry ice is tossed in to sublimate into CO2 gas while the winemaker is free to take care of other tasks rather than babysit the tank. Regardless of the method chosen, the goal is the same to blanket the tank - especially the bottom portions that the wine will begin to fill up - with an inert gas that is heavier than oxygen and therefor pushes it out of the way.
With the tank taken care of, however, there is still more work to do. What about the hoses that will be used to move the wine through the filter or pump - they are filled with ambient (20.946% oxygen) air and we don't want to have the wine come into contact with that and then pump gallons of oxygenated air into our carefully prepared tank! The hoses have to be gassed as a result, with the open end that isn't connected to the gas cylinder pointed in an elevated position so the heavier gas can best push out the ambient oxygen. Alternatively the hoses can be hooked up to the pump and the process can begin by pumping water so the hoses are entirely filled with H20 before hooking them up to the wine, but this wastes water and makes it awkward to judge when the hose has wine in it rather than water so it can be connected to the new tank.
All in all it is not necessarily a complicated threat to prepare for, but it does take a great deal of time to think through all the possibilities and sort out what is best. So long as you are keeping oxygen away from the wine, I have not heard of major reasons why one method would be better than another, so it mostly comes down to personal and winery-to-winery preference. At Fox Run we prefer to gas our tanks using CO2 rather than the more expensive Argon or Nitrogen, especially because you can 'smell' when a tank has been adequately gassed with CO2 as opposed to the other two.
After all this work to keep the wine ensconced away from oxygen, you can probably understand why winemakers treat corked bottles as such a personal affront. When we spend this much time on even the smallest aspects of protecting the wine, having it destroyed by something (a tainted cork) you have no control over - or even a chance to detect - is thoroughly disheartening. But cork taint is a story for another day....
By: Kelby Russell, Winemaking Team
*To be fair, we do try to stay friendly with oxygen during the height of vintage when the winey might be filled to dangerous/suffocating capacity with C02 from fermentations.
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